1. Field of the Invention
The present invention relates generally to a lubricating structure of a hydraulic clutch, and more particularly to a lubricating structure for supplying a lubricating oil from a hydraulic pump to clutch plates in a hydraulic clutch for allowing the transmission of power between a first rotating shaft and a second rotating shaft.
2. Description of the Related Art
In general, a lubricating oil is sealed in a speed reducer or the like having a hydraulic clutch to reduce frictional resistances at a rotating portion and a sliding portion and prevent heating, seizure, corrosion, etc. Unless the lubricating oil is sufficiently supplied to all clutch elements, the above problem including seizure may arise. Japanese Patent Laid-open No. Hei 9-42317 discloses a lubricating structure for supplying a lubricating oil from a hydraulic pump driven by a first rotating shaft (input shaft) to clutch plates in a hydraulic clutch for allowing the transmission of power between the first rotating shaft and a second rotating shaft (output shaft).
In the lubricating structure disclosed in this publication, a lubricating oil passage for introducing the lubricating oil from the hydraulic pump to the hydraulic clutch is formed between the inner circumference of a pump driving member for driving the hydraulic pump and the outer circumference of the second rotating shaft. According to this structure, it is not necessary to form a lubricating oil passage inside the second rotating shaft, so that a working cost can be reduced and the sectional area of the lubricating oil passage can be increased to thereby enhance the lubricating effect of the hydraulic clutch. However, this structure has a problem such that it is difficult to uniformly supply the lubricating oil to all the clutch plates engaged by splines with the outer circumference of a cylindrical clutch hub and the inner circumference of a clutch housing, because the lubricating oil from the lubricating oil passage is supplied to the inside of the clutch hub.
Another clutch structure of a hydraulic clutch having a plurality of slits has been proposed. The slits are formed in a flange and a cylindrical portion of the clutch hub so as to be spaced in the circumferential direction for the purpose of uniformly supplying the lubricating oil to all the clutch plates. This lubricating structure has exhibited an effect to some extent, but cannot achieve the primary purpose of uniformly distributing the lubricating oil to all the clutch plates.
More specifically, when the hydraulic clutch is engaged, the clutch hub is rotated, so that the lubricating oil supplied is scattered through the slits of the cylindrical portion of the clutch hub to the outer circumference thereof by a centrifugal force. As a result, the lubricating oil reaching the slits of the flange is greatly limited, and the clutch plates especially about the flange cannot therefore be sufficiently lubricated.
It is therefore an object of the present invention to provide a lubricating structure of a hydraulic clutch which can supply a lubricating oil uniformly and sufficiently to all the clutch plates.
In accordance with an aspect of the present mention, there is provided a lubricating structure of a hydraulic clutch including a drum-shaped clutch housing connected to a first rotating shaft, the clutch housing having a first spline formed on the inner circumference thereof; a clutch hub connected to a second rotating shaft coaxial with the first rotating shaft, the clutch hub having a cylindrical portion having a first end and a second end, a flange formed integrally with the cylindrical portion near the first end, and a second spline formed on the outer circumference of the cylindrical portion; a plurality of first clutch plates axially slidably engaged with the first spline of the clutch housing; a plurality of second clutch plates axially slidably engaged with the second spline of the clutch hub; clutch engaging means for engaging the first and second clutch plates with each other; and lubricating oil supplying means for supplying a lubricating oil into an internal space defined inside of the cylindrical portion of the clutch hub from the side of the second end; the cylindrical portion of the clutch hub having a plurality of first lubricating oil passages for radially outwardly introducing the lubricating oil from the inner circumference of the cylindrical portion to the outer circumference thereof; the flange of the clutch hub having a plurality of second lubricating oil passages for axially introducing the lubricating oil from the internal space toward the first end of the cylindrical portion.
With the above lubricating structure, the lubricating oil from the lubricating oil supplying means is scattered radially outward by the centrifugal force of the rotating clutch hub to collide with the inner circumference of the cylindrical portion of the clutch hub and be diffused therealong, and a part of this lubricating oil is supplied through the first lubricating oil passages formed through the cylindrical portion to the clutch plates mounted on the cylindrical portion of the clutch hub.
The remaining lubricating oil is supplied through the second lubricating oil passages formed through the flange to the back side of the flange, and is next supplied through the first end of the cylindrical portion to the clutch plates mounted about the flange of the clutch hub. Accordingly, the lubricating oil can be sufficiently supplied also to the clutch plates about the flange where the supply of the lubricating oil is insufficient in the prior art. As a result, a sufficient amount of lubricating oil can be uniformly supplied to all the clutch plates.
Preferably, the clutch hub is formed of sintered metal. Accordingly, the dimensional accuracy of the clutch hub can be improved, and the first and second lubricating oil passages can be easily formed. More preferably, the cylindrical portion of the clutch hub further has a plurality of third lubricating oil passages for radially outwardly introducing the lubricating oil passed through the second lubricating oil passages to the outer circumference of the cylindrical portion.
The ratio of the area of the first lubricating oil passages to the area of the inner circumferential surface of the cylindrical portion on the side of the second end with respect to the flange is smaller than the ratio of the area of the third lubricating oil passages to the area of the inner circumferential surface of the cylindrical portion on the side of the first end with respect to the flange. With this configuration, a sufficient amount of lubricating oil can be uniformly supplied to all the clutch plates.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.